Method for forming light pipe structure with high quantum efficiency

A method for forming an image sensor, the method comprising:

• forming a photodetector in a substrate;
• depositing a lower dielectric structure over the photodetector;
• performing a first etch process on the lower dielectric structure to define an opening in the lower dielectric structure;
• depositing a lower etch stop layer over the lower dielectric structure and lining the opening;
• depositing an upper dielectric structure over the lower etch stop layer such that the upper dielectric structure fills the opening;
• performing a patterning process to define a light pipe opening within the upper dielectric structure and over the photodetector, wherein the patterning process comprises a second etch process that is performed at a higher power than the first etch process;
• and
• forming a light pipe structure within the light pipe opening.

A method for forming an image sensor, the method comprising:

• depositing a lower dielectric structure over a substrate;
• forming a lower etch stop layer over the lower dielectric structure such that the lower etch stop layer comprises a U-shaped segment over a photodetector disposed within the substrate;
• depositing an upper dielectric structure over the lower etch stop layer;
• forming an upper etch stop layer over the photodetector such that the upper etch stop layer continuously vertically extends from a top surface of the upper dielectric structure to a point below a top surface of the lower etch stop layer;
• and
• forming a light pipe structure over the photodetector such that the light pipe structure contacts sidewalls of the upper etch stop layer and sidewalls of the lower etch stop layer.